Maybe the max is level 70 on the upgrades? I would definitely be interesting in hearing updates on how high you go on your upgrades.
I figured those two were the main two to invest in. I also upgrade Longer Slow Tower, More Starting Cash, and extra lives, I believe those five in total would be the most benificial. What are your thoughts about that?
How much is it to upgrade for you now, from level 29 to 30?